Questions and postings pertaining to the usage of ImageMagick regardless of the interface. This includes the command-line utilities, as well as the C and C++ APIs. Usage questions are like "How do I use ImageMagick to create drop shadows?".
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xberg
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by xberg » 2017-12-22T01:23:59-07:00
Hi,
I want to transform any JPG into a 50% transparent PNG.
I found how to make a specific color fully transparent with:
Code: Select all
magick convert 1.jpg -fuzz 8%% -transparent white 1.png
But I don't want this: I want all the JPG to be a 50% opaque PNG.
Thanks
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snibgo
- Posts: 10018
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- Location: England, UK
Post
by snibgo » 2017-12-22T01:44:11-07:00
Code: Select all
magick in.jpg -alpha set -channel A -evaluate set 50% +channel out.png
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xberg
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Post
by xberg » 2017-12-22T01:47:17-07:00
Thank you!
Great!! What's the +channel at the end for?
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snibgo
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Post
by snibgo » 2017-12-22T02:05:53-07:00
"-channel A" means "apply all following operations to just the Alpha channel". "+channel" means "set the default, which is that all following operations apply to all channels".
In this case it is superfluous, but good practice is: whenever you have a "-channel", you should always have a "+channel" somewhere.
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xberg
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by xberg » 2017-12-22T02:18:17-07:00
Thanks! Great explanations
